Can you trace a money order - 's possible that the prohibition against chain letters involving the sending of money through the mail has been misconstrued as a general prohibition against sending cash via mail for any reason (to the extent that such an act is often claimed to be a felony), but the frequently asked questions (faq) section of the usps web site explicitly acknowledges that cash may be sent through the u. Anything more than a small amount of cash via mail has never been a particularly good idea, primarily because if such a shipment is lost, stolen, or destroyed in transit, neither the sender nor the intended recipient may have any recourse to recover the funds. . postal service (usps) for purposes that are inherently illegal, such as operating lotteries through the mail or evading taxes or laundering money, but there is no general prohibition on mailing cash from one place to another for legitimate purposes. To get a money order, you often need to get cash, wait in line, wait for a customer service representative (who is doing their best) to complete the transaction, and get the money order into the mail.